Using Rain water for water change? ??

[Nageltribe]

I rently moved to M.U.D #5 in Cypress. I'm thinking about starting a rain collection barrel to use for my 55 tank water changes. I searched the forum but did not find anything exactly on point for this topic. IS Houston RAIN water generally safe to use? Does anyone have experience doing this? Should I use rainwater exclusively or just mix it with tap water? I'm wondering if there are significant pollutants that a test kit will not show? I would change over slowly to avoid shock, but I'm thinking I'd like to get off tap water all together eventually.

The water here is so hard and loaded with chlorine that everything is coated with scale and the test kit shows the GH /KH are off the chart. I've cleaned the cover twice with vinegar already In 6 months.

2nd year Noob appreciates any help!!!
1 pleco, 1 Cuckoo catfish, 1 neon tetra, red flame Gourami, 2 Blood Red Parrots, Blue lobster. 2 Bosemani rainbows, 1 teal rainbow .

[troy tucker]

i think the biggest prob. you will find. It doesn't rain here enough to keep up with year round water changes. As for pullutants? I'm pretty sure falling through Houstons air. There will be some pullution.
I used to age water but seachem and prime will fix the water. With out all the work or you could use RO/ID.